(Reuters) – Bird flu has public health officials on alert after an unprecedented spread in dairy cows in the United States this year. Four dairy workers also tested positive in the country.
A particularly serious variant of the H5N1 strain has been spreading around the world in animals since 2020, causing lethal outbreaks in commercial poultry and sporadic infections in other species, from alpacas to domestic cats. Until this year, it had never infected cows.
Different strains of bird flu have been found in Australia and Mexico in humans, while different H5 subtypes are also present around the world in both animals and humans, in countries such as China and Cambodia.
Most human cases have reported exposure to poultry, live poultry markets or dairy cattle before infection, but scientists are concerned that the virus could mutate that makes it more easily spread from person to person, which could trigger a pandemic. The World Health Organization says the risk to people is low at this time.
Below are the occurrences of various types of bird flu viruses that have been found in humans this year.
U.S:
The first known cases of infected dairy cattle occurred in Texas in March and are now in dairy herds in 12 states. The U.S. Department of Agriculture said testing so far indicates that the virus detected in the cows is the same H5N1 virus that affects wild birds and commercial poultry flocks. The four dairy workers who tested positive for the virus this year had mild symptoms such as conjunctivitis or conjunctivitis.
The H5N1 virus in the United States belongs to clade 2.3.4.4b, genotype B3.13, a genotype detected only in North America so far, the European Food Safety Agency said in a scientific report.
MEXICO:
A resident of Mexico has died from the first known cases of H5N2 bird flu in humans, the WHO said on June 5. Mexico’s government said chronic illness, not bird flu, was the cause of death. The person had no known exposure to animals.
AUSTRALIA:
The WHO said on June 7 that a child with H5N1 bird flu reported by Australia had traveled to Kolkata, India. Genetic sequencing showed the virus was a subtype of H5N1 and part of a strain circulating in Southeast Asia and detected in previous human and bird infections.
Australia is separately dealing with three outbreaks of different strains of the virus on poultry farms – H7N3, H7N8 and H7N9 – which authorities say likely reached farms through wild birds.
INDIA:
The WHO reported on June 11 a case of human bird flu infection caused by the H9N2 subtype in a four-year-old child in the state of West Bengal in eastern India. It was the second human H9N2 bird flu infection in India, following a case in 2019, the agency said. Although the H9N2 virus normally tends to cause mild illness, the United Nations agency said more sporadic human cases could occur as this is one of the most prevalent avian flu viruses circulating in poultry in different regions.
VIETNAM:
Vietnam reported that a 21-year-old student died from H5N1 bird flu in March. He had no underlying medical conditions, but had been exposed to wild birds while hunting a few weeks before the onset of symptoms. No contact with dead or sick birds was reported at the time.
Vietnam also reported an outbreak of H9N2 in a 37-year-old man, EFSA said.
CAMBODIA:
The Southeast Asian nation and neighbor of Vietnam reported five human cases of H5N1 as of June 20.
CHINA:
China this year detected human cases caused by the H5N6, H9N2 and H10N3 strains, with two fatal cases of H5N6 in Fujian province. Both cases had exposure to poultry before the onset of symptoms, EFSA said.
The H10N3 bird flu case was the third reported globally.
GERMANY:
Germany has reported a rare outbreak of highly pathogenic H7N5 bird flu on a farm in the western part of the country, near the border with the Netherlands, the World Organization for Animal Health said July 4. It was the first outbreak of H7N5 anywhere in WOAH. public data.
(Reporting by Sybille de la Hamaide, Tom Polansek, Cassandra Garrison, Peter Hobson, Jennifer Rigby, Leah Douglas and Caroline Stauffer; Editing by Bill Berkrot)
